PURPOSE: To strengthen a connecting strength, to simplify a method of manufacturing and to reduce the cost of production by heating and working to reduce thickness of a fitted material in which a core material is fitted with an outer layer material.
CONSTITUTION: Outside a columnar or cylindrical, e.g. a pure titanium core material 11, e.g. Al outer layer material 12 is fitted to form the composite material 10. Then, for the purpose of preventing relative movement between the outer layer material 12 and the core material 11, one end of the composite material 10 is connected and restrained mechaniclly or metallurgically mutually. Then, after heating the outer layer material 12 by a high-frequency heating furnace 20, the composite material 10 is worked by a inclined rolling mill 4 or an Asser mill type to reduce the thickness. Therefore, a thin intermetallic compound layer is formed on the interface to get rid of exfoliations and the connecting strength is strengthened. Moreover, because the manufacturing method is simple, the production cost is reduced.